ORA-16191: Primary log shipping client not logged on standby

Stanby database stop working with below error.

ORA-16191: Primary log shipping client not logged on standby
PING[ARCl]: Heartbeat failed to connect to standby 'STDBY'. Error is 16191.

Redo shipping client performing standby login
OCISessionBegin failed -1
.. Detailed OCI error val is 1017 and errmsg is 'ORA-01017: invalid username/password; logon denied
'
*** 2009-02-25 14:41:21.470 61287 kcrr.c
Error 1017 received logging on to the standby
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Check that the primary and standby are using a password file
and remote_login_passwordfile is set to SHARED or EXCLUSIVE,
and that the SYS password is same in the password files.
returning error ORA-16191
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Check if you have pwd file at both primary and stanby.

If sys passwd is changed at primary, copy password file from primary to standby

Restart the standby and start recovery.